Hi teeraniti, I have a Hydroflame in my Caravel
as well. I am pretty happy with it. It works quite well. Even when it is below freezing out, it will keep the trailer at about 68 deg. More if I turn it up higher.
I understand why you would like to keep it.
I have not had to touch my valve, that thankfully works fine.
Some things you might want to check out if you are handy.
Do you have propane coming in to the heater from the supply line ? If not there may be a kink in the line.
The main burner orifice could be clogged. It can be cleaned
Your thermocouple could be bad. No way to tell if you can't get the pilot to light. You can get a new thermocouple. The generic ones will work fine, just make sure the bulb on the end is long enough to reach the pilot flame. Take your old one with you when you go to buy one.
You pilot light orifice could also be clogged. It can be cleaned too.
The valve should be easy to turn. Remember you have to push it in then turn. If it is hard to turn, the valve may have gotten some moisture in it and corroded. In that case you will have to locate a new one. You can't rebuild these valves to my knowledge.
I am not sure if you can still get new valves. There may be other propane appliances that use the same valve. My suggestion is that you find a RV appliance shop. We have one in Portland. That is all they do. The name is Laurelhurst Heating and Cooling. I don't have the number handy. A propane appliance shop will work too. It doesn't have to be an RV shop. Propane appliances pretty much all work the same. One thing you can try is take the knob off and spray some penetrating lubricant down the shaft and let it sit a while. That may loosen things up.
Or you could find a RV repairman that is willing to work on it for you.
I hope this helps some.
I do have an extra valve but I believe it is in the same condition as yours. I'll have to check.
Just another thought here, Google Singletons RV Salvage. They may have what you need. Take a picture of it and email it to them with an explanation of what you need.
There are a couple other RV Salvage places around but the names escape me right now.